This invention relates to an acceleration control system for automobiles provided with a continuously variable transmission commonly referred to as a CVT.
With the recent marked development of hydraulic pump/motors having high efficiency, it has become possible to greatly improve the performance of a hydrostatic transmission referred to as an HST or a hydromechanical transmission referred to as an HMT which both comprise a combination of such hydraulic pump/motors. Now the time is becoming ripe for application of these transmissions to automobiles which require a transmission having a high performance characteristic.
Since the engine with one of the transmissions of the above-mentioned types can be started with the reduction ratio set to infinity, theoretically they do not require a clutch or a torque converter. This is a great advantage. However, if the continuously variable transmission of such characteristics as mentioned above is used in an autmobile having a conventional driving system, a trouble is likely to occur during the acceleration stage immediately after the automobile has started to move. In particular, since the reduction ratio of the transmission is close to infinity at the start of the engine, if the accelerator pedal is stepped in a usual manner, the pressure of the hydraulic pump becomes excessive so that the relief valve opens, with resulting loss of energy and racing of the engine.
Accordingly, the primary object of the invention is to completely eliminate the above-mentioned and other difficulties in an acceleration control system for automobiles which employ a continuously variable transmission such as either of the above-mentioned types in connection with its engine the output of which is controlled by the driver operating the accelerator.
The invention will be described in detail with reference to the accompanying drawing.